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[aprssig] APRS data via perl-to-tnc

Stephen H. Smith wa8lmf2 at aol.com
Sun Oct 2 17:40:54 UTC 2011

On 10/2/2011 11:59 AM, Arnie Shore wrote:
> Re "What ya trying to achieve"  I want to get an APRS data stream from some 
> arbitrary station onto our CAD's MySQL db.
> Currently, we pull a given station's data from aprs.fi <http://rs.fi> despite 
> that station's sitting maybe six feet away. An ARES/RACES team user has asked 
> me to look into avoiding the latency and error-proneness inherent to the long 
> path.  (Agreed that we shudda done that years ago!)

Wow!  That is really the long way around!

Local station heard off-air by nearby igate station --> igate passes packets to 
APRS-IS server --->APRS-IS server passes data to all other APRS-IS 
servers-->one of the APRS-IS servers passes data to aprs.FI (which is logged 
into an APRS-IS server just like any other end-user)-->end-user then pulls data 
off APRS-fi for local use.

At least, you could have an app logged directly into  APRS-IS server, with a 
filtered feed for specific stations.   This at least would eliminate the 
latency of APRS.fi batching up data for a specific station and then sending it 
to you on request, as well as numerous additional router hops.    The filtered 
feed would be continuous and immediate (i.e. you automatically get each 
transmission as it is sent), within a few seconds of the original RF 
transmission without having to keep requesting chunks of data from APRS-fi.

If you choose a relatively nearby (physically) APRS-IS server  to log  into, 
you can vastly reduce the number of router hops and potential delays/losses of 
packets, as well as cutting out the additional middleman of APRS.fi.  (All data 
heard by all igates is replicated on ALL APRS-IS servers within a second or two 
of the original transmisssion - it doesn't matter which APRS-IS server you use.)

If the area of operations for the command post is such that it can hear 
everything of interest directly off-the-air (or via local digipeaters), you 
could bypass the Internet system entirely, assuming your CAD system can pull 
data from IP-based sources.

One of the features that is unique (as far as I know) to UIview is it's TCP/IP 
"local server".   Everything UIview hears from the attached radio/TNC 
--and/or-- it's Internet APRS-IS login is replicated at a local TCP/IP server 
port.  In turn, other APRS clients and applications on the same LAN can connect 
to to the local server in exactly the same way they would to the Internet 
APRS-IS.     This local server port is fully bi-directional.  Other users on 
the LAN can send messages either to RF (via the UIivew host's radio/TNC), 
--or-- to stations on the APRS-IS --or-- to other stations on the LAN.

The local server feature was specifically built into UIview for the kind of 
operation you are dealing with:  To allow multiple work stations in an EOC to 
share a single radio/TNC and a single Internet connection.

The local server can accommodate almost any number of TCP/IP-enabled APRS 
applications, either on the same machine, or on multiple machines on the same 
LAN.  (Or even from remote locations via the Internet, with appropriate port 
forwarding settings in your Internet router.)

I have personally had a copy of UIivew with it's local server running supply 
TCP/IP data to:
o     Two other copies of UIview (so I could have simultaneous multiple mapping 
views going)
o     APRSpoint (MapPoint-based APRS client)
o     APRS Messenger (HF PSK63-based soundcard APRS client) - passes 30-meter 
HF APRS activity to the Internet via the UIview host's Internet connection.)
o     UI-Instant Messager (APRS text-messaging-only client patterned after AOL 
Instant Messenger)
o     Two more copies of UIview running on two other machines on my LAN (one a 
WiFi-connected netbook).

All at the same time, with only one TNC and one Internet connection.



Stephen H. Smith    wa8lmf (at) aol.com
=== Now relocated from Pasadena, CA back to 8-land (East Lansing, MI) ===
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

=====  Vista & Win7 Install Issues for UI-View and Precision Mapping =====

*** HF APRS over PSK63 ***

"APRS 101"  Explanation of APRS Path Selection & Digipeating

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